Effects of probiotics and amprolium on performance, lesion scores, oocyst shedding, and histopathological changes in Eimeria tenella-infected broiler chickens.

Background and aim: Coccidiosis caused by Eimeria tenella significantly impairs poultry health and productivity, prompting the search for alternative or complementary therapies to conventional coccidiostats. This study investigates the prophylactic and therapeutic efficacy of a probiotic complex of Lactobacillus, Bifidobacteria, Enterococcus, and Streptococcus, alone or in combination with amprolium, against E. tenella infection in broiler chickens.

Materials and methods: A total of 90 broiler chickens were randomly allocated into six experimental groups (n = 15/group). Group 1 served as the uninfected control, while Group 2 comprised infected but untreated controls. Group 3 received probiotics at a concentration of 1 mg/mL, and Group 4 was treated with amprolium at a dosage of 20 mg/kg. Group 5 was administered a combination of probiotics (1 mg/mL) and amprolium (20 mg/kg), whereas Group 6 received prophylactic treatment with probiotics (1 mg/mL). All groups except the uninfected control were challenged orally with 2 × 10⁴ sporula-ted E. tenella oocysts. Growth performance was monitored on days 15, 21, and 28. Lesion scoring, oocyst shedding, and histopathological examinations were conducted on day 28. An in vitro sporulation assay evaluated the inhibitory potential of treatments on oocyst development.

Results: In vitro, the probiotic-amprolium combination significantly reduced oocyst sporulation rates (5.86%). In vivo, amprolium and prophylactic probiotics significantly improved body weight gain and feed intake (p < 0.05) and reduced oocyst shedding. Lesion severity and parasite stage counts were significantly lower in the amprolium group; however, the combination group exhibited unexpectedly higher lesion scores. Mortality was highest in the amprolium and untreated groups (20%) but absent in the combination group, suggesting differential immunomodulatory effects. Histopathological analysis confirmed reduced intestinal damage in groups treated with amprolium or prophylactic probiotics.

Conclusion: Amprolium monotherapy and prophylactic probiotic supplementation were effective in mitigating E. tenella-induced pathology and improving broiler performance. Probiotics alone provided moderate benefits, while their post-infection therapeutic use or co-administration with amprolium did not yield superior results. These findings underscore the prophylactic value of probiotics and warrant further studies to optimize combination regimens under field conditions.